Zuckerberg made the rounds on Capitol Hill meeting with senators ahead of the hearing Tuesday afternoon, which lawmakers anticipated to stretch on for hours. He is also slated to testify Wednesday before the House Energy and Commerce Committee, where he is expected to apologize for the Cambridge Analytica data leak.

She noted that the Facebook CEO has apologized for his company’s missteps but added: “Stop apologizing, it’s time to make a change.”

Cortez Masto said that in the 14 years since Facebook was founded "I haven’t seen much change” regarding the company's promises to improve on data privacy.

The company’s privacy woes date back to 2007 when Facebook promised to do better after making user purchases public with its Beacon advertising platform.

Cortez Masto called into question Facebook’s compliance with the Federal Trade Commission (FTC) consent decree the company agreed to in 2011 over previous privacy violations.

Zuckerberg challenged her that Facebook had taken steps to comply with the FTC before she cut him off.

“It’s time to make a change. It’s time to address privacy issues,” she said.

– Ali Breland

GOP senator: I don’t want to regulate Facebook, but ‘by God, I will’

6:50 p.m.

Sen. John KennedyJohn Neely KennedyMORE (R-La.) grilled Zuckerberg over the company’s privacy practices, threatening that Congress would impose regulations on the company if it doesn’t improve its policies.

“I don’t want to vote to have to regulate Facebook, but by God I will. A lot of that depends on you,” Kennedy told Zuckerberg in the fifth hour of a marathon hearing on Capitol Hill during which the Facebook chief addressed the Cambridge Analytica controversy.

“You’ve done a lot of good,” Kennedy said. “But our promised digital Utopia, we have discovered, has mine fields. There are some impurities in the Facebook punch bowl, and they’ve got to be fixed. And I think you can fix them.”

Kennedy predicted Tuesday that the controversy will result in a “whole bunch of bills” being introduced to regulate Facebook, saying that it would largely be up to Zuckerberg whether they pass.

“You can go back home, spend $10 million on lobbyists and fight us, or you can go back home and help us solve this problem,” Kennedy said.

The Republican senator suggested that Zuckerberg overhaul the company’s user agreement so that the average American can understand it.

“Your user agreement sucks,” Kennedy said. “The purpose of that user agreement is to cover Facebook’s rear end, it’s not to inform users of their rights.”

Meanwhile, Zuckerberg defended the company, saying that it already allows users to delete their data and control who it is shared with.

– Morgan Chalfant

Zuckerberg indicates plans to use AI to monitor discriminatory practices

6:09 p.m.

Zuckerberg suggested during the hearing that Facebook plans to use artificial intelligence to better monitor discriminatory practices on the platform after conceding that it struggles to monitor all of the content.

Though Markey repeatedly tried to frame his inquiry as a yes or no question, Zuckerberg evaded the questioning, only going so far as to say that he liked the concept of increased privacy controls but declining to say whether such standards should be required by law.

“Senator, in general I think that principle is exactly right, and I think we should have a discussion about how to best codify that,” the Facebook CEO said.

Markey grew increasingly frustrated as Zuckerberg gave similar answers about legislation that would offer tougher privacy protections for children online.

Zuckerberg’s answers are notable because protections similar to what Markey is proposing will soon be required under European Union law. The new regulations, set to go in effect next month, will only apply to EU countries, but the CEO has said Facebook will offer new privacy controls to all of its users.

– Harper Neidig

Facebook stocks soar during testimony

5:06 p.m.

Facebook shares closed 4.5 percent higher on Tuesday during Zuckerberg's testimony, suggesting that Wall Street was encouraged by his performance.

The stock's strength could also indicate that the finance sector may not take seriously some lawmakers' threats to regulate Facebook and other tech giants.

It was a rare positive sign for a company that has seen its shares plummet after revelations about the Cambridge Analytica data scandal last month followed by calls for regulation.

Zuckerberg defended Facebook as a “platform for all ideas.” At the same time, he acknowledged that Facebook’s presence in the liberal Silicon Valley could cause such concerns to arise.

“There are a great many Americans who I would say are deeply concerned that Facebook and other tech companies are engaged in a pervasive pattern of bias and political censorship,” Cruz said.

Cruz cited a 2016 Gizmodo report alleging that Facebook suppressed conservative news outlets, as well as the recent revelation that Facebook barred Trump supporters Diamond and Silk from the platform after deeming their content “unsafe to the community.”

Zuckerberg called the concerns “fair” and said he has worked to “root out” any political bias in the company’s work.

“I understand where that concern is coming from, because Facebook and the tech industry are located in Silicon Valley, which is an extremely left leaning place,” Zuckerberg said.

“This is actually a concern that I have, and that I try to root out at the company — is making sure that we don’t have any bias in the work that we do,” he added. “I think it is a fair concern that people would at least wonder about.”

"I think that might be what this is all about," Durbin said. "Your right to privacy, the limits of your right to privacy and how much you give away in modern America in the name of 'connecting people around the world.’ "

Zuckerberg argued that Facebook gives users control over who sees the content they post.

"I think everyone should have control over how their information is used," he said.

The Facebook CEO also said he “believes” the company may have been served with a subpoena from the special counsel’s office.

Facebook previously acknowledged that the company handed over information to Mueller on political advertisements purchased by Russia-linked accounts, but there have been few public details of the extent of the social media giant’s cooperation in the investigation.

“I want to be careful here because our work with the special counsel is confidential,” Zuckerberg said Tuesday. “I know that we are working with them.”

– Morgan Chalfant

Zuckerberg says fighting disinformation campaigns is top priority in 2018

3:20 p.m.

Zuckerberg said one of his “biggest regrets” is that he did not identify a Russian disinformation campaign early enough during the 2016 presidential campaign.

“This is one of my top priorities in 2018,” he added.

Zuckerberg said he has “more confidence” Facebook will succeed in protecting from such abuse because the platform had a “better record” in other recent overseas elections such as those in France and Germany.

“We’ve deployed new A.I. tools that do a better job of identifying fake accounts,” he told the lawmakers, saying they are trying to “remove accounts before they could contribute significant harm.”

– Olivia Beavers

Facebook didn’t notify FTC about Cambridge Analytica data scandal

3:15 p.m.

Zuckerberg told lawmakers that Facebook did not notify the Federal Trade Commission (FTC) of the Cambridge Analytica data scandal when it discovered the issue in 2015.

Facebook said it told the data firm in 2015 to delete the information it had improperly obtained on millions of users, but only publicly disclosed the issue last month when reports emerged that the company did not delete the data despite being told to do so.

The FTC is currently investigating Facebook for possibly violating a 2011 consent decree by allowing Cambridge Analytica to access the data.

When asked by Nelson whether he thought Facebook had an “ethical obligation” to notify users whose data had been accessed, Zuckerberg reiterated that the company considered it a “closed case” in 2015.

“We considered it a closed case,” Zuckerberg said. “In retrospect, that was a mistake.”

– Morgan Chalfant

Zuckerberg says no plan to make users pay

3:10 p.m.

Under questioning from Sen. Bill Nelson (D-Fla.), Zuckerberg said that Facebook doesn't have any plans to offer a paid service that would let users opt-out of having their data collected.

"We think offering an ad-supported service is the most aligned with our mission of trying to help connect everyone in the world, because we want to offer a free service that everyone can afford," Zuckerberg said. "That’s the only way we can reach billions of people."

Some critics have argued that Facebook should offer a subscription service that would give users an alternative to having their data collected for targeted ads.

Zuckerberg also stressed that Facebook believes the data it collects belong to the users.

"The first line of our terms of service say that you control and own the information and content you put on Facebook," he said.

– Harper Neidig

Zuckerberg apologizes

3:02 p.m.

Zuckerberg opened his remarks to the Senate Judiciary and Commerce committees hearings with a contrite tone, apologizing for his company’s recent missteps.

“It’s clear now that we didn’t do enough to prevent these tools from being used for harm as well. That goes for fake news, foreign interference in elections and hate speech, as well as developers and data privacy. We didn’t take a broad enough view of our responsibility, and that was a big mistake,” Zuckerberg said, unilaterally shouldering the responsibility for Facebook’s mistakes.

“It was my mistake, and I’m sorry. I started Facebook, I run it, and I’m responsible for what happens here,” he said.

Zuckerberg spent the rest of his remarks detailing previously released details about the Cambridge Analytica scandal including steps his company is taking to improve consumer data.

– Ali Breland

Leaders hint at potential regulations on Facebook

2:55 p.m.

Both Senate Commerce Committee Chairman John Thune (R-S.D.) and Bill Nelson (D-Fla.), the ranking member, hinted at the possibility of imposing regulations on tech companies to help protect user data.

“In the past, many of my colleagues on both sides of the aisle have been willing to defer to tech companies’ efforts to regulate themselves,” Thune said in his opening remarks. “But this may be changing.”

Later, Nelson pressed Facebook and other social media companies to "get your act in order."

“If Facebook or other online companies will not or cannot fix the privacy invasions, then we are going to have to. We, the Congress," Nelson said.

The longtime senator said in addition to Russia’s efforts to interfere in the presidential election, millions of people’s personal information was used without their knowledge “in order to manipulate public opinion.”

Estimates of individuals who had their personal information taken without their consent by Cambridge Analytica is 30 million more than the initial estimates at 57 million,she said.

She additionally pointed out that special counsel Robert Mueller has charged the Information Research Agency, a Russia-tied group, with trying to intentionally “harm Secretary Clinton’s campaign” through adds on Facebook that may have had as many as 157 million viewers.

– Olivia Beavers

Thune homes in on data privacy, transparency

2:45 p.m.

Senate Commerce Committee Chairman John Thune (R-S.D.) used his opening remarks to stress that Facebook and other tech companies need to explain how they will take greater responsibility of what happens on their platforms, including with respect to data privacy and transparency.

“How will you protect users’ data?” Thune asked ahead of Zuckerberg's testimony. “How will you inform users about the changes you are making? And how do you intend to proactively stop harmful conduct, instead of being forced to respond to it months or years later?”

He raised questions about the steps Facebook has said it will take to better guard user data from third-parties looking to exploit it, noting that some of the actions could “actually serve to enhance Facebook’s own ability to market such data exclusively.”

– Morgan Chalfant

Zuckerberg enters the room

2:30 p.m.

Mark Zuckerberg entered the packed hearing room to a waiting crowd of photographers, staffers and reporters for the first of two marathon hearings.

Facebook officials including the company’s top lawyer, Colin Stretch, were already in the room sitting behind Zuckerberg’s witness dais.

Several lawmakers including Sen. John Kennedy (R-La.), who has been critical of Facebook in recent weeks, approached Zuckerberg and exchanged brief words before he sat down for Judiciary Chairman Chuck Grassley’s (R-Iowa) opening remarks.

– Ali Breland

Grassley says data privacy a top concern

11:57 a.m.

In an op-ed published in Fortune, Senate Judiciary Committee Chairman Chuck Grassley (R-Iowa) lays out what he wants Zuckerberg to address: specifically, how Facebook is addressing growing consumer data privacy concerns.

“Consumers must have the transparency necessary to make informed decisions about whether to share their data and how that data can be used — be it in political campaigns or in tailored ads,” Grassley wrote. “That kind of transparency has been woefully absent, which is why it’s necessary to hear directly from Zuckerberg on what he sees as Facebook’s most pressing problems and what his company is doing to fix them.”

While Grassley did not outright call for regulations on technology companies meant to address data security, he voiced the need for private tech firms and Congress to work in tandem to set “new rules of the road” for consumer data. At minimum, he wrote, tech companies should work to provide more transparency around how consumer data is collected and used.

“The status quo no longer works,” Grassley wrote. “As innovation continues, the industry needs to work with Congress to determine if and how we need to strengthen privacy standards.”

The lawsuit was filed by seven people who were swept up in the trove of data that wound up in the hands of Cambridge Analytica, a company that did work for the Trump campaign ahead of the 2016 election.

The class action was filed on behalf of all American and British users among the 87 million who were unwittingly swept up.